XMLHttpRequest

MDN Reference

The XMLHttpRequest.readyState property returns the state an XMLHttpRequest client is in. An XHR client exists in one of the following states:

The XMLHttpRequest response property returns the response's body content as an ArrayBuffer, a Blob, a Document, a JavaScript Object, or a string, depending on the value of the request's responseType property.

The read-only XMLHttpRequest property responseText returns the text received from a server following a request being sent.

The XMLHttpRequest property responseType is an enumerated string value specifying the type of data contained in the response.

The read-only XMLHttpRequest.responseURL property returns the serialized URL of the response or the empty string if the URL is null. If the URL is returned, any URL fragment present in the URL will be stripped away. The value of responseURL will be the final URL obtained after any redirects.

The XMLHttpRequest.responseXML read-only property returns a Document containing the HTML or XML retrieved by the request; or null if the request was unsuccessful, has not yet been sent, or if the data can't be parsed as XML or HTML.

The read-only XMLHttpRequest.status property returns the numerical HTTP status code of the XMLHttpRequest's response.

The read-only XMLHttpRequest.statusText property returns a string containing the response's status message as returned by the HTTP server. Unlike XMLHttpRequest.status which indicates a numerical status code, this property contains the text of the response status, such as "OK" or "Not Found". If the request's readyState is in UNSENT or OPENED state, the value of statusText will be an empty string.

The XMLHttpRequest.timeout property is an unsigned long representing the number of milliseconds a request can take before automatically being terminated. The default value is 0, which means there is no timeout. Timeout shouldn't be used for synchronous XMLHttpRequests requests used in a document environment or it will throw an InvalidAccessError exception. When a timeout happens, a timeout event is fired.

The XMLHttpRequest upload property returns an XMLHttpRequestUpload object that can be observed to monitor an upload's progress.

The XMLHttpRequest.withCredentials property is a boolean value that indicates whether or not cross-site Access-Control requests should be made using credentials such as cookies, authentication headers or TLS client certificates. Setting withCredentials has no effect on same-origin requests.

The XMLHttpRequest.abort() method aborts the request if it has already been sent. When a request is aborted, its readyState is changed to XMLHttpRequest.UNSENT (0) and the request's status code is set to 0.

The XMLHttpRequest method getAllResponseHeaders() returns all the response headers, separated by CRLF, as a string, or returns null if no response has been received.

The XMLHttpRequest method getResponseHeader() returns the string containing the text of a particular header's value.

The XMLHttpRequest method open() initializes a newly-created request, or re-initializes an existing one.

The XMLHttpRequest method overrideMimeType() specifies a MIME type other than the one provided by the server to be used instead when interpreting the data being transferred in a request.

The XMLHttpRequest method send() sends the request to the server.

The XMLHttpRequest method setRequestHeader() sets the value of an HTTP request header. When using setRequestHeader(), you must call it after calling open(), but before calling send(). If this method is called several times with the same header, the values are merged into one single request header.